New Methods For Error Identification And Diagnosis Of CNC Machine Tools

Error identification and error diagnosis of CNC machine tools have been a key means to verify the overall performance of the machine. Specifically, error identification results provide a theoretical basis for error compensation and correction, error diagnosis results provide scientific judgment for inspection and regular maintenance of machine tool. Therefore, the paper has made a corresponding analysis about error identification and error diagnosis, which is based on the double ball bar (DDB) measurement platform. Meanwhile, some new methods are put forward.Firstly, geometric errors including21items are analyzed on three-axis vertical machining center in order to create a spatial error model. This model provides a theoretical basis for the study of the error trajectory. Then paper analyzes the phenomenon that error trajectory is changed when different error term is present and the problem for the quantification of error value according to geometric error, clearance error and dynamic error shown by DDB software. At the same time, the method that can identify the error is put forward though the trajectory model directly. Secondly, roundness error algorithm, consisting of least square circle (LSC), minimum circumscribed circle (MCC), maximum inscribed circle (MIC) and minimum zone circle (MZC), will be analyzed in detail by computational geometry. Finally, error measurement experiments are conduct on the gantry CNC machine tools using DDB. Which roundness error algorithm is applied to DDB software by comparing with evaluation results calculated by four methods mentioned above. Subsequently the method on integrated error diagnosis for large CNC machine tools is present.The significance of this thesis mainly has two aspects. On the one hand, the data processing method could be understood in DDB’s software, known as "black box" in the DDB measurement platform. The research may help know the key technology of software and develop the new products. On the other hand, it may provide some reference methods for diagnosing error of large CNC machine tools. The work has practical significance.